Financial Instruments and Fair Values - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	$ 11,947,000		$ 11,947,000		$ 5,591,000
Net unrealized loss on valuation of swap agreement	(14,367,000)	$ (10,864,000)	(12,973,000)	$ (30,235,000)
Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	12,000,000		12,000,000
Designated as Hedging Instrument | Cash Flow Hedging
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net unrealized loss on valuation of swap agreement	(14,400,000)	$ (10,900,000)	(13,000,000)	$ (30,200,000)
Amount expected to be reclassified within twelve months			2,500,000
Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional amount	790,000,000		790,000,000
Accounts payable and accrued expenses | Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements liability	$ 11,900,000		$ 11,900,000		5,600,000
Prepaid expenses and other assets | Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap agreements asset					$ 600,000